The invention relates to a hot gas filter for separating solid matter carried along in high temperature gases and waste gases.
The hot flue gases produced in incinerators contain considerable amounts of suspended solid matter which must not be released into the atmosphere. This applies above all to incinerators in which radioactively, biologically and bacterially contaminated waste material is burnt. It is therefore recommended to ensure treatment of the hot flue gases immediately after they leave the incinerator in order to avoid fouling or contamination of the waste gas system. However, the flue gases leave the incinerators at temperatures ranging between 700 and 1000 degrees centigrade and it is therefore rather difficult to develop filters which ensure a high filtering effect, low draft losses, a sufficiently long service life and which can easily be reactivated. In nuclear process engineering, several approaches have been made to solve this problem by using filter cartridges made of burnt, porous ceramic material in the form of long cylinders, with one end being closed and the other end open for admission of the hot flue gases to be treated and provided on the open end of the cylinder with a radially projecting flange for holding the filter cartridges which are inserted in the openings of a sieve bottom. However, sealing of the filter cartridges in the sieve bottom gave rise to various problems due to the fact that the sieve bottom and the openings change their dimensions with rising temperatures, which means that particularly in case of differing thermal expansion coefficients for sieve bottom material and the ceramic material of the filter cartridges, gaps and passages may form through which untreated flue gases may penetrate if no special sealing such as asbestos cords etc. is provided. It is evident that draft losses, i.e. unintended pressure drops, in such filter cartridges are considerable and therefore high-capacity waste gas fans are required in the waste gas system. Furthermore, the removal of solid particles retained inside the porous wall, renders cleaning and regeneration of the filter cartridges rather difficult and worn-out filter cartridges must be crushed and the remaining parts are still of relatively high weight. Last but not least, these filter cartridges are, especially in the proximity of the radial flanges, highly sensitive to mechanical stresses and strains. For the above specified reasons, the need for an improved hot gas filter wherein the above problems are solved, is very urgent.